1. Field of the Invention
This invention relates to a transmitting apparatus and a transmission method for transmitting user data.
2. Description of the Related Art
In recent years, multiple input multiple output (MIMO) technology has been attracting attention as a technique to increase transmission rate (refer to, for example IEEE 802.11n “Part 11; Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specification” Oct. 29, 2009). To be more concrete, the MIMO technology allows transmission of different data sets to a user terminal respectively from multiple antennas. Thus, it is possible to increase transmission capacity and to improve transmission reliability.
In the meantime, the reachability of the user data may degrade because transmission or reception of the user data may fail due to a factor such as a dead spot or change in the characteristics of transmission path.
As techniques to enhance the reachability of the user data, there are known a technique that performs retransmission control of user data, a technique that decreases the transmission rate of user data by use of adaptive modulation control, and the like.
However, the retransmission control of user data causes a decrease in the throughput due to retransmission delay, while the adaptive modulation control causes a decrease in the throughput due to a decrease in the transmission rate. Accordingly, the technique to increase the reachability of user data still has room for improvement.
In this respect, this invention has been made to solve the aforementioned problems, and the objective of the present invention is to provide a transmitting apparatus and a transmission method each of which is capable of increasing the reachability of user data.